Operating I nstructions—Type 422 AC-DC
Channel 1
(reference) Channel 2
Fig. 2-19. Measuring phase difference.
Fig. 2-20. High resolution phase-difference measurement with
increased sweep rate.
of the graticule (see Fig. 2-19). Each division of the
graticule represents 45° of the cycle (360° ^ 8 divisions =
45°/division). The sweep rate can be stated in terms of
degrees as 45°/division.
45°/division -MO = 4.5°/division. Fig. 2-20 shows the same
signals as used in Fig. 2-19 but with the X10 MAG switch
pulled out. With a horizontal difference of six divisions, the
phase difference is:
11. Measure the horizontal difference between corres
ponding points on the waveforms.
12. Multiply the measured distance (in divisions) by
45°/division (sweep rate) to obtain the exact amount of
phase difference.
EXAMPLE. Assume a horizontal difference of 0.6 divi
sions with a sweep rate of 45°/division as shown in Fig.
2-19.
horizontal ... ,
nu r^-cx w magnified sweep rate
Phase Difference = difference X , . . ,
(division) (degrees/div)
Substituting the given values:
Phase Difference = 6 X 4.5°.
The phase difference is 27°.
Using the formula:
Phase Difference
horizontal
difference
(divisions)
sweep rate
A (degrees/div)
Substituting the given values:
Phase Difference = 0.6 X 45°
Common-Mode Rejection
The ALG ADD feature of the Type 422 can be used to
display signals which contain undesirable components.
These undesirable components can be eliminated through
common-mode rejection. The precautions given under Alge
braic Addition should be observed.
1. Connect the signal containing both the desired and
undesired information to the INPUT 1 connector.
The phase difference is 27°.
High Resolution Phase Measurements
More accurate dual-trace phase measurements can be
made by increasing the sweep rate (without changing the
VARIABLE TIME/DIV control setting). One of the easiest
ways to increase the sweep rate is with the X I0 MAG
switch. The magnified sweep rate is determined by dividing
the sweep rate obtained previously by the amount of sweep
magnification.
EXAMPLE. If the sweep rate were increased 10 times
with the magnifier, the magnified sweep rate would be
2. Connect a signal similar to the unwanted portion of
the Channel 1 signal to the INPUT 2 connector. For exam
ple, in Fig. 2-21 a line-frequency signal is connected to
Channel 2 to cancel out the line-frequency component of
the Channel 1 signal.
3. Set both Input Coupling switches to DC (AC if DC
component on input signal is too large).
4. Set the vertical Mode switch to ALT. Set the
VOLTS/DIV switches so the signals are about equal in
amplitude.
2-27
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